Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year					$ 1,800
Post-Retirement Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year					$ 233
Service cost	$ 9	$ 10	$ 26	$ 31
Interest cost	36	33	109	98
Expected return on plan assets	0	0	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	0	0
Net amortization of net (gain) loss	(4)	0	(12)	0
Net Periodic Benefit Cost	41	43	123	129
Defined Benefit Plan, Plan Assets, Contributions by Employer			188
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	304	347	913	1,041
Interest cost	866	798	2,599	2,395
Expected return on plan assets	(896)	(991)	(2,689)	(2,972)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	1	1
Net amortization of net (gain) loss	389	362	1,168	1,085
Net Periodic Benefit Cost	$ 663	$ 516	1,992	$ 1,550
Defined Benefit Plan, Plan Assets, Contributions by Employer			$ 1,767